更新导航抽屉中当前突出显示的片段

Question

When I open a new fragment from the nav drawer it correctly highlights it but when I press the back button it doesn't update the highlighted element so I was thinking of using navigationView.setCheckedItem(); but that needs an int and I have no clue on what to put there since I have no idea if I can use the back stack somehow or not.

At the moment onBackPressed only has

    public void onBackPressed() {
    DrawerLayout drawer = findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    }else{
        super.onBackPressed();
    }
}

What am I doing wrong?

EDIT: I solved by doing one of the worst things I could have imagined, in each fragment :

@Override
public void onResume() {
    super.onResume();
    auIsInFront = true;
}

@Override
public void onPause() {
    super.onPause();
    auIsInFront = false;
}

And then in MainActivity :

@Override
public void onBackPressed() {
    DrawerLayout drawer = findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    }else{
        super.onBackPressed();
        NavigationView navigationView = findViewById(R.id.nav_view);
        if (isInFront){
            navigationView.setCheckedItem(R.id.nav_home);
        }else if (standardIsInFront){
            navigationView.setCheckedItem(R.id.nav_standard);
        }else if (auIsInFront){
            navigationView.setCheckedItem(R.id.nav_au);
        }
    }
}

I know it's horrible but that's the only thing that I could think of

Answer 1

As the documentation says setCheckedItem takes view id as argument. You should use it like this:

navigationView.setCheckedItem(R.id.yourMenuItem);

Now You want to create some variable that keeps last activity / menu item and then change highlith. Example:

int lastMenuID;
public void onBackPressed() {
  DrawerLayout drawer = findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
      drawer.closeDrawer(GravityCompat.START);
    }else{
      int thisID = /*[this menu item]*/;
      navigationView.setCheckedItem(lastMenuID);
      lastMenuID = thisID;
      super.onBackPressed();
    }
  }